Expanding tap



C. H. DOMMETT.

EXPANDINGTAP. I APPLICATION FILED JUL'YZ. 1920.

Patented D60. 12, 1922.

3 SHEETS-SHEET l- D WMW/ d 2 ed d d A C. H. DOMMETT.

EXPANDING TAP. g APPLIYCATION FILED .IULY2. I920. 1,438,367. a Patented Dec.12,1922.

3 SHEETS-SHEET 2.

C. H. DOMME'TT.

EXPANDING TAP.

APPLICATION FILED 1ULY2. 1920.

1,438,367. Patented Dec. 12,1922.

I 3 SHEETS-SHEET 3.

E-Jwvewtoz Patented Dec. i922- HENRY DOIVIIJIEIT, F SWINDON, ENGLAND, ASSIG-NQR TO FRANK SIDDALL,

OF DETROIT, MICHIGAN.

EXFA'NDING TAP.

Application filed Ju1y2, 192D. Seria1 No. 393,678.

(GRANTED UNDER THE IROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. 11-, 1313.)

To all whom it may concern: 7

Be it known that I, Crmnnns HENRY DOM- Mn'r'r, a subject of the King of Great Britain,

and a resident of Swindon, county of Wilts, England, have invented certain new and useful Improvements in Expanding Taps (for which I have filed an application in England July 3, 1917, Patent No. 116,574), of which the following is a full, clear, concise, and exact description, such as will enable others skilled in the art to which the invention relates to make and use the same, reference being made therein to the accompanying drawings, which form a part of this specification.

This invention relates to expanding taps,

for screw cutting, of the type in which a plurality of die plates placed in a plurality of slots formed axialwise and radiating from the centre of a holder, are expanded by a spindle moved axially therein, a spring being arranged to contract the die plates on the spindle being moved in the opposite direction.

It is usual in practice to use taps of this vtype to cut threads and to use what are termed solid taps to size up the hole to a fine limit of diameter, especially in the man ui'acture of explosive shells. On the with- :50 drawal oi the solid tap the friction is such as to cause considerable wear to the threads reducing its life considerably. v

This invention has for its object the pro vision of means for adjusting the diameter of a tap, of the type described, which is specially necessary, after the cutting edges have been re-ground, in order that a very fine limit in diameter, when required,can be obtained, thereby dispensing with the necessity icing a solid tap. i iccording to this invention a floating spindle is provided with two truncated conical shaped members with their smaller diameters facing one another, each member lli'il'lflgi slots and cam-shaped surfaces arranged axiali'vise on their surfaces for the 6X pension and contraction of the dies. One of the truncated conical shaped i'i'iembers is adjusted endwise for increaslng or decreasingv the effective cutting diameter of the die plates.

In a modified form one truncated conical shaped member is fixed or formed on the end of a spindle, means being providedfor giving endwise adjustment to the spindle.

The end of the holder has an annular recess for the reception of a plurality of coiled springs each having two projecting ends. Each spring when placed in position, has each of its ends bearing on the side of separate dies toiorce them toward the truncated conical shaped member, or members.

The invention is illustrated with the aid of the accompanying drawings, Figure 1 being longitudinal section showingpart of the shank in elevation, also the handle and die plates. Figure 2 half plan and half section through line 22 of Figure 1.

Figure 3 inverted plan of the head of Figure 1 in the direction of the arrow 0, when the cover plate is removed.

Figure 4 elevation of the spindle with the truncated cone shaped members. Figure 5 half plan and half section through line 5--5 01" Figure 4.

Figure 6 elevation andFigure 7 plan of one of the die plates.

Figure 8 sectional elevation of the tap when used with one truncated cone shaped member on the spindle.

Figure 9 side, and Figure 10, end elevation, and Figure 11 plan of the wedge shaped member for giving endwise adjustment.

Figure 12 plan of a portion of the handle showing the circular end. Figure 13 moditication of the tap, illustrated by Figure 8, for use with a hand tool. I

Figure 1% part elevation and section of a device for automatically moving the truncated cone shaped member, or members, into position for the dies to be retracted.

Figure 15 plan of Figure 14:.

The holder is in the form of a circular bar a having a head a of increased diameter, while the end of the small or shank portion is formed either in the shape of a square a in cross section for the purpose of enabling the holder to be operated by an ordinary tool constructed for the purpose, or with a circular end to adapt it to be used in a machine.

The head a ot the holder has a circular recess of axially in one end leading to near the base thereof, leaving a concentric wall a. An annular recess is also formed inthe concentric wall a on the end of the head leaving an inner concentric-wall a around the central recess 0 and the outer concentric wall a around the annular recess a. The central recess a is carried beyond the end of the slots a while the annular recess a 'is carried down to a depth suihcient to enable coiled springs b to be inserted as hereinafter described. The inner concentric wall a, i. e., between the central and annular recesses a and a projects beyond the end of the head, the latter being flat and at right angles to the axis of the holder. A hole a is formed axially inthe case of the central recess (4 and connects to an elongated hole a on the shank a. The elongated hole a has two parallel sides and is at right angles to the axis ofthe holder, and of sui'icient length axialwise vof the l'iolder to enable the spindle carrying'the truncated cone shaped 'nembers to be moved enowise.

In" the end of the outer concentric wail a of the' heald of the holder are four slots at" axialwise of 'theholder' so that the cutting edges of the die plates '0' placed therein, would, as they wear on their face edges (3", be spaced equal distances apart circumferentially. The length of each of the slots axialwise, is equal'to the length of each of the dies 0. The bases of the slots a" are at right angles to the centre line of the holder, each slot being carried through the inner co n'centricwall a. A portion of the outer circumferential surface of the head is cut awayat a onthe cutting side 0 of each of the die plates 0, for clearance purposes. Each ofthe' d-ie plates 0'is"ofequal dimensions and rectangular inform, the outer wall formed in the us ual'way with teeth for screw cutting or'chasinig. The back wall of each die plate a recedes at an angle longitudinally from each side of its centre, to fit the outer faces of the truncated cone shaped members, one longitudinal half 0 of the back wall be 111 formed with a concavity across it for the length of 'the die plate to enable it to can tact'wi th the circumferential surfaces of the truncated cone shaped members (Z and d, while'the other half 0 recedes at an angle to adapt it to contact with the inclined portions (5? of the slots of each of the truncated cone shaped members (land all;

The members fore'xpanding the die plates are in th'eforni of two truncated cones (Z and CZ 'with"their"smaller' diameters facing each other. These truncated cone shaped members are placed on the end of a spindle the inner-truncated cone shaped. member (Z being 'fi xed and of greater length than the outer one (1 and having a portion (Z of its larger end cylindrical and adapted to be guided by the end of the central recess a, while the outer truncated cone shaped member'ii is adapted to be moved endwis-e 'towards the inner'truncated cone shaped member any the action'of'a nut working over the screw threaded end of'the spindle e A feather c is fixed on the spindle for pre venting the outer truncated cone shaped member CZ from rotating thereon while permitting it to be moved endwise. A spring Z2 is placed on the spindle 0 between the two truncated cone shaped members (i and J to keep them apart. When it is desired to reduce the effective diameter of the dies by release of the nuts 7" and f the resiliency of the spring ensures that the outer adjustable truncated cone shaped member (5 shall follow them. Each of the truncated cone shaped members cl and d has four slots formed lengthwise in its circumferential face, the base a of each slot convex, to seat the concave back 0 of the die plate 0, and of width to equal.

the width of the concave back portion 0 of the die plate 0, one side al of the slot being parallel to the radius line while the other side d of the slot is inclined outwards to the horizontal to agree with the angle of the receding edge on the back of the die plates 0. i

One end of the spindle e carrying the truncated cone shaped member (Z is enlarged as at c, the diameter of which is less than that of the larger diameter of the inner truncated cone shaped member (Z and adapted to pass into the hole a formed axially through the base of the central recess a of the holder, a hole 6 screw threaded, being formed in the side of the spindle near its end.

@ne end of the handle for operating, is of smaller diameter than the length of the elongated hole (4 aXialwise of the holder, and has its screw threaded portion 9 attached to the screw threaded hole 0 in the side of the spindle e.

@ne side face of each die plate '0 has a circular recess 0" therein while the other has a slot 0 for the purpose of receiving the protruding ends 3) of a coiled spring I) placed in the annular recess a" between the die plates 0, and adapted to contact them when the spindle oscillated by means of zhe handle g, into the position for the back ends of the die plates to contact with the base of the recesses of the two truncated cone shaped members (5 and d. The outer trunca-ted cone shaped member 03 is adjusted towards the inner truncated cone shaped member 63 by means of a nut f, and a check nut 7", working over the threaded portion of the spindle c. The outer wall of the recess has grooves a formed axialwise with the holder to partially seat the coiled portion of the springs 7). The arrangement of the coiled springs in an annular recess, with their two ends in engagement with one side of each of the two adjacent die plates, ensures that if one or two of the springs should fail, and if the remainder have their ends engaged with one side of each of the can adjust themselves to an even the base of the slots position by means of screw threaded bolts or studs 71. A hole 7:? is made through the centre of the base of the circular recess through which passes the nut f, when placed in position on the spindle the inner or end face of the nut f abutting against the larger end of the outer truncated cone shaped mem ber (Z.

until the concave portions 0 are seated by theaction of'the coiled springs 22 against the circumferential wall of the truncated cone shaped members 0? and fl;

On the wearing of the teeth, on the die plates 0, for forming the screw threads, or on its being found necessary toincrease or decrease the diameter over the die plates, the necessary adjustment is made by the nut f forcing the outer truncated cone shaped member d towards, or permitting it to be retracted from, the inner truncated cone so that when the spindle e of the handle 9, the die plates 0 are forced outwards against the action of the coiled springs 72 to the desired extent.

In the improved tap the combined spindle and truncated cone shaped members are free to move axialwise within certain limits in order that the back edges of the die plates bearing in of the truncated cone shaped members so as to ensure the cutting edges protruding the requisite distance beyond the circumferential surface of the head, v

One of the truncated cone shaped mem bers being adjustable on the spindle enables the range of the tap to be varied within cer tain limits thereby allowing o'tfine adjustments; y

In a modification the-adjustment of the dies for use in holder. used with a hand tool or on a machine can be made with a. spindle having oscillating and longitudinal adjustments but with single truncated cone shaped member asrepresented in Figure 8. The single truncated, cone shaped member A is formed with slots Similar to that deshaped member (Z is oscillated, by means Onthe'oscillation of the spindle, by means and seating itself in an enlargen T termined i limits.

scribed for the two truncated cone shaped members, as shown in Figures 2, 4. and 5 the drawings, length which increased in order to contact with most, if not all of the back surface of with the exception of the the dies 0, which have a single instead of a double inclined surface 0 as indicated in Figure 8 of the draw'ings. The spindle e is of one diameter from the end of the truncated cone shaped member d with the exception of its central portion 6 which is of smaller diameter to reduce frictional contact in the h ole a of the shank of the holder. The hole: a in the holder is oritendechover that described for the tap with two truncated cone shaped members, toineeta hole a carried diametrically through the shank and atright angles thereto. A wedge shaped member 0 having one end circular and the other: shaped to agree with the body portion. which'has flat sides parallel to each other and top and bottom curved to the same radius as the circular end, is placed in position throughthe end of the hole a, made diametrically tothe shank so that its inclined surface 0 contacts with the inclined surface p of a bearing piece 7). The bearing piece 79 is circular to fit and longitudinally of the shank and has one end 39 slotted to form an incline 7') while the side walls fit over the sides 0 of the central portion of thew-edge shaped member, and its other end contacting with the end a? of the spindle. The sides of the hearing piece,

having the incline, fitting over the sides 0 member prevents it of the Wedge shaped spindle is part ally from twisting when the rotated. v i

The inner or rear end. a of the spindle is square in cross section to make a working fit in the squarehole 9 in the boss on the end of the handle 5/. The boss 9' on tne end of the handle 9 is circular witl'r a square hole 9 axially through it. 1The shank of the holder has an elongated hole (L at llglll) angles to its axis connecting with the. hole a axialwise of the shank of the holder to admit of the boss of the handle pas in into to be adjusted in either; direction in the hole (7 in the boss oi the handle within predehe holcyr in the shanl: of the holder is elongated .in a. horizontal plane at right angles tqits axis. while its slide in the hole a i len th axialwise is such to permit of the handle-beingoscillated.

. The handle is tormed in two parts that portion having the boss 5/ withthe square partially hole 9 is at one end of the bar while the other end portion h flange g around-its circumference perm ing oil a sleeve 9' bcving placed loosely over it, the extreme end portion oi? the bar being screw threaded at g over which the other part oi; the handle 5 is placed.

Each end oi" the hole a made diametrically to the shanl: is sc ew threaded to receive screw threaded studs r and r to ad'- just the wedge shaped member in order that the spindle may forced in one direction to increase, and be moved by resilient means in the opposite direction to decreasethe eilective diameter of the cr ng edges of the dies. The smaller end o oe truncated cone shaped member (Z has a projecting pin a secured thereto or iormed thereon adapted to pass inside the coilsofa spring 8. The inside face of the cover plate it its central portion closed, instead of open as previously described, and is formed with a circular recess 72, to receive the coiled spring 8, the purpose of the latter being to force the spindle towards the rear end of the holder when the dies have to be reset by'the' endwise movement 01" the spindle for a smaller diameter.

It will be seen that on the slackening of the left hand screwed nut r it gradually comes away from the centre of the shank of the holder, and the right hand screwed stud r can be screwed into the shank forcing the wedge shaped member towardsthe left hand stud permitting the coiled spring a in the recess of the cover to force the spindle towards the back end of the holder thereby reducing the effective diameter of the cutting edges the dies, and vice versa.

In the case of a hand driven tap-see Figure l3the hole in the recess of the holder is carried at a reduced diameter through the shank, its outer portion'screw threaded to receive a screw threaded stud T which, when screwed into the hole, bears on the end of he spindle and forces it forward to expand the dies to increase the effective diameter;

but when the screw stud 1" is unscrewed, or withdrawn from the shank of the holder, the effective diameter or" the dies is decreased the action of the coiled spring 5* forcing the of the holder.

' The shank is provided with a screw threaded hole, right angles to its axis, to receive a screw threaded stud r which, when tightened, prevents the stud r in the end of the shank from working back dui'ing'the time the tap is in use.

In the modification of the improved tap for use on a power driven machine, I place on the shank a device, which, when the tap has nearly reached the depth required to be threaded, will move he handle, and with it the spindle, for the truncated. cone shaped spindle towards the back end rotating or oscillating on the shank by means off a key a arranged longitudinally and protruding from the circumference or the same, the outside of the sleevescrew threaded with a left hand threat-lb Over the screwed portion of the sleeve is placed a collar 76?. having its interior surface screw threaded to adapt it to fit the threaded por tion of the sleeve. The collar is split horizontally at is? for a portion of its circumference and is also split longitudinally and the ends on each side of the split portion are provided with an outwardly projecting flange 76 having a hole in each, one flange having a screw threaded hole to receive the shank a of a bolt head k which is threaded into it to draw the flangestogether and tighten the collar on the sleeve. The lower end of the collar has an outwardly extending flange 72?.

The flange of the finger or cam being inclined at the requisite angle so that when thedie plates are extended and the tap about to be'usedto out the threads in the walls or" the hole of any article, the position of the automatic device would be such that on the tap reaching to near the depth to which the threads are required to be out, the flange on the collar would be in'contact with the'article and during thereinainder of the endwise movement ot-thetap the -device would gradually tr avel-endwise in the holder until the inclined side of the cam or finger, contacts with the sleeve or roller on the handle and moves the spindle so that the truncated cone shaped member, or members,

'would be moved into position to enable the die'plates to be retracted automatically by the coiled springs and the tap withdrawn from the hole in the article by an endwise movement. i

' The split collar being screw threaded on the sleeve enables .it to be adjusted to act with various depths ofholes within reasonable'limits. l l A plurality of elongated holes 76 can be made through the collar at its junction with the flange for the purpose of passing lubricant to the tap. v

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare thatwhat I claim is 1. In an expanding tap, the combination of a holder having radial slots and'an axial Lessee? bore, die plates seated in said slots and movable radially therein, a spindle rotatable and axially movable in said bore, said spindle having a tapered portion with cam surfaces adapted to force said plates outwardly by rotation of said spindle, resilientmeans for retracting said plates upon reverse rotation of said spindle, and means for adjusting the spindle axially and retaining the same in its adjusted positions.

2. In an expanding tap, the combination of a holder having radial slots and an axial bore, die plates seated in said slots and movable radially therein, a spindle rotatable and axially movable in said bore, said spindle having a tapered portion with cam surfaces adapted to force said plates outwardly by rotation of said spindle, resilient means for retracting said plates upon reverse rotation of said spindle, and means for adjusting the spindle axially and retainthe same in its adjusted positions comprising transverse wedge means engaging the spindle and spring means operative in opposition thereto.

8. In an expanding tap, the combination of a holder having radial slots and an axial bore, die plates seated in said slots and movable radially therein, a spindle rotatable and axially movable in said bore, said spindle having a plurality of oppositely tapered portions with cam surfaces adapted to force said plates outwardly by rotation of said spindle, means for retracting said plates upon reverse rotation of said spindle, and means for adjusting said tapered portions to vary the effective diameter of the die plates.

Bi tap as set forth in claim 3 including resilient means inserted between said tapered portions, for the purpose described.

5. A. tap as set forth in claim 1, the resilient retracting means comprising a plurality of springs seated in recesses in said holder and each spring having its opposite ends engaging adjacent die plates.

6. In an expanding tap, the, combination of a holder having radial slots and an axial bore, die plates seated in said slots and movable radially therein, a spindle in said bore rotatable and axially movable therein, said spindle having on its periphery spaced cams tapered longitudinally of the spindle and adapted by partial rotation of the spindle to force said plates outwardly, springs in engagement with and adapted to retract the said plates, and means for positioning the spindle axially of the holder to determine thereby the effective diameter of the said die plates.

7. In an expanding tap, the combination of a holder having radial slots and an axial bore, die plates seated in said slots and radially movable therein, a spindle rotatably positioned in said bore, oppositely tapered cams on said spindle adapted by partial rotation of said spindle to force said die plates outwardly and by axial adjustment to determine the effective diameter of said tap when expanded, and means for adjusting said cams axially of the holder.

8. In an expanding tap, the combination of a holder, die plates supported therein for radial movement, means "for moving said plates outwardly to increase the effective diameter of said tap, and means operative after a predetermined working movement of said tap to engage said moving means and return the same positively to its original position thereby permitting the said plates to be retracted.

9. In an expanding tap, the combination of a holder, die plates supported therein for radial movement, a spindle adapted by partial rotation to move said plates outwardly, a handle on said spindle, and means adapted to engage with a fixed abutment after a predetermined working movement of said tap and operating upon said handle to move said spindle to a position permitting the die plates to be retracted.

10. In an expanding tap, the combination of a holder, die plates supported therein for radial movement, a spindle adapted by partial rotation to move said plates outwardly, and means adapted to engage with the work after a predetermined working movement of said tap to actuate said spindle to a position permitting the retraction of said plates comprising a device longitudinally movable on said holder but non-rotative relative thereto and cam means on said device adapted to engage a part fixed to said spindle to cause rotation thereof.

11. In an expanding tap comprising a holder, radially movable die plates, and expanding means therefor including a handle extending laterally from said holder and movable in one direction to expand. the tap and in the opposite direction to permit retraction of the said plates, means for moving the handle in the last-mentioned direction comprising a sleeve longitudinally slidable but non-rotatable on said holder, the forward end of said sleeve engageable with the work and the rear end having means adapted to actuate said handle.

12. In an expanding tool, the combination of a holder, dies radially movable therein, a central spindle, cam devices actuated by rotative movement of said spindle to force said dies radially outward to determine thereby the working diameter of said tool, and means carried by said spindle and adjustable relatively thereto to vary the initial position of said dies.

In testimony whereof I afiix my signature.

CHARLES HENRY norm/mi" 

